Add Microsoft Application Insights output plugin (#4010)

plugins/outputs/application_insights/diagnostic_message_subscriber.go

@@ -0,0 +1,12 @@
+package application_insights
+
+import (
+	"github.com/Microsoft/ApplicationInsights-Go/appinsights"
+)
+
+type diagnosticsMessageSubscriber struct {
+}
+
+func (ms diagnosticsMessageSubscriber) Subscribe(handler appinsights.DiagnosticsMessageHandler) appinsights.DiagnosticsMessageListener {
+	return appinsights.NewDiagnosticsMessageListener(handler)
+}